DEVELOPMENT AND CHARACTERIZATION OF PANI/RHA/EPOXY NANOCOMPOSITES FOR HIGH
PERFORMANCE APPLICATION
T.LAKSHMIKANDHAN
1,V.L.CHANDRA BOSS
21,2
Associate Professor,Department of Chemistry, BIST, BIHER, Bharath University,Chennai-73
lakshmikandhan.che@bharathuniv.ac.in,Chandraboss.che@bharathuniv.ac.in,
Abstract
In the present work different ratio of PANI/epoxy were synthesized. The molecular structure of the RHA, PANI, PANI-RHA was confirmed by FTIR spectroscopic techniques. The morphology study of PANI-RHA composites was characterized by TEM analysis. Data obtained from thermogravimetric analysis indicate the PANI-RHA composites possess the highest thermal stability. The water absorption studies shows the decreases the water absorption stability.
Key words: PANI, Epoxy, Rice husk ash, TEM.
Introduction
Epoxy coating are being extensively used in the industrial areas, because of high strength,
good adhesion to different substrates[1-6], and good resistance against industrial corrosive
environments (1). But it has some disadvanges of, easy to brittle, hydrophilic nature and coast
effect. So that toPreventing of coated surfaces of substrates from above disadvanges, which is
used for electrically conductive polymers are have promising materials for anti-corrosion
properties. Such aspolypyrrole (PPy)[7-11], polyaniline (PANI) and their derivations havebeen
studied due to their electrical conductivity[12-16]. Among this the polyaniline (PANI) has been
found to be very effective material for corrosion protection and they have two different ways to
prevent corrosion of substrates,in the one hand[17-21], PANI acts as a physical barrier inpaint film which prevents penetration of corrosive ions across thecoating and the other hand, and it passivates the surface of the metallicsubstrate by formation of Fe
2O
3on the surface of iron (2, 3).
The electrical property of polyaniline is an important factorwhich could be modified by the addition of inorganic fillers suchas metal oxides, semiconducting materials (4). The synthesis of inorganic fillers having high cast and time process are high. Thus, it would be useful to find inexpensive sources of such materials as Rice husk ash (RHA), it’s very low cost and high silica content (85 wt. %). Its have many potential advantages, e.g. abundant renewable source, high specific strength, stiffness, non abrasive and less hazardous to health[22-26].
Hence in the present work, the synthesis of PANI- RHA has prepared and characterized.
It has been incorporated into epoxy resin in different weight percentages and added Aradur 140(polyamidoimidazoline) as a room temperature curing agent. Finally the composite solution applied to mild steel and cured for one week. After curring, the studies of water uptake, morphological and anti corrosion resistance. Theproperties of resulting coated materials have been analyzed and discussed[27,28,29].
Materials
Aniline (monomer),ammonium per sulphate, hydrochloric acid wereObtained from Merck, India and double distilledwater was used for complete work.Epoxy resin (diglycidyl etherofbisphenol- A,DGEBA,withEEW182-192,viscosity)andAradur 140(polyamidoimidazoline) curing agent were obtained from Huntsman (India).
Preparation of Rice husk ash (RHA)
Rice husk ash is a solid powder obtained after burning of rice husk followed bywashing with distilled water and dried in an oven at about 60 ˚C for 2 h. Then washed withacetone and hydrochloric acid (2 M) to remove dirt and other contaminants present in themand then dried in oven at about 60 ˚C for 4 h. Samples of rice husk were heated at 500 ˚C for5 h in a muffle furnace, to obtain rice husk ash[30-34].The removal of surface impurities enhances the surface roughness thus generatingmore hydroxyl groups and other reactive functional groups on the surface (5).
Synthesis of polyaniline doped rice husk ash (PANI-RHA)
The synthesis of polyaniline doped rice husk ash was carried out by taking 50 ml of 1MHCl containing 2ml aniline into 250ml RB flask that was placed in an ice bath, adding an amount of 1g RHA under sonication for 2h andthen adding drop wiseammonium per sulfate solution in 50ml of 1M HClat 0-5
oC for 12h[36-41]. The precipitates were collected on a Buchner funnel andrepeatedly washed with distilled water. Then, the product was dried under vacuum conditionat70
oC for 8 h (2).
Preparation of PANI-RHA epoxy composites
DGBEA was mixed with different weight percentages of PANI-RHA (0, 1.0, 3.0,5.0 and 7.0
wt%) using ethanol as a solvent with constant stirring for 12h at 500rpm. After the complete
dissolution, the stoichiometric amount of curing agent (Aradur 140) was added separately and
the stirring was continued for 15min to obtain homogeneous blend. The PANI-RHA modified
epoxy was cured with Aradur 140 and coated on mild steel using bar coater to a thickness of
100±10μm. The coated specimens were kept for 7days to cure completely at 30
oC. Finally the
specimens were tested for their corrosion resistant behavior by immersing them in 3.5% NaCl for
30 days (ref). Schematic representation of reaction shown in Figure 1[42-45].
Surface preparation of the test specimen.
Mild steel specimens cut from the same batch of sheet stock of (3cm × 2cm) 6cm
2area ( C-0.04%; Si-0.01%;Mn-0.17%; P-0.002%; S-0.005%; Cr-0.04%; Mo-0.03%; Ni-1.31%; Fe- balance)were used as a substrate material for the present study. The specimenswere degreased with acetone and placed them in the desiccators for conditioning for overnight. Then thespecimens were subjected to sand blasting at a pressure of 100-psi through the nozzle to get theappropriate crevices. The particle size of the sand was 80 mesh. The distance between thesubstrate and the blaster was maintained at 2 feet. The blasted sample specimens were cleanedand kept them in the desiccators for conditioning.
Characterization
Fourier transform infrared (FT-IR) spectra were recorded on a Perkin Elmer 6X FTIR
spectrometer. Thermogravimetric analysis (TGA) was carried out, using the DSTA 409 PC
analyzer(Netzsch Gerateban GmbH). X-ray diffraction patterns were recorded at room
temperature, by monitoring thediffraction angle 2θ from 10 to 70˚ as the standard, on a Rich Seifert (Model 3000) X-raypowder diffractometer. The surface morphology of the coated surface of the samples wasexamined, using a scanning electron microscope (SEM; JEOL JSM Model 6360). A JEOLJEM-3010 analytical transmission electron microscope, operating at 80 kV with a measuredpoint-to-point resolution of 0.23 nm, was used to characterize the phase morphology of thedeveloped nanocomposites. TEM samples were prepared by dispersing composites undersonication in ethanol and mounted on carbon-coated Cu TEM grids and dried for 1h at 70
°Cto form a film of < 100 nm.
Water Absorption property
The water absorption behavior of the samples was tested as per ASTM D 570 for 30days at 30
oC. The percentage of water by the specimen is calculated using equation.
% of water absorption = (W
2-W
1) X 100/W
1Where, W
1is the initial weight of the sample and W
2is the weight of the sample after immersion in water for 30 days at 30
oC.
Results and discussion
FT-IR analysis of RHA, PANI and PANI-RHA
Figures 1-3 shows FT-IR spectra of RHA, PANI and PANI-RHA.From the FT-IR
spectrum, RHAillustrates the broad band and sharp peaks observed at 3510 and1641cm
-1are due
to the stretching and bending vibrations mode of Si-OH band it shows in Figure (1). The
stretchingvibration of peaks at1098 and 805 cm
-1corresponding to Si –O–Si and Si-O
linkage.The FTIR spectrum of PANI in Figure (2)show stretching vibration bands attributable to
the quinonoid and benzenoid functional groups at 1650 and 1540 cm
-1respectively. In addition, a
stretching band assigned to C–N also appears at 1393cm
-1. The C-H deformation is observed at1116 and844cm
-1respectivelyand shows the polymerization of aniline.These peaks can also be seen in the spectra of PANI-RHA nanocomposites and all bands are slightly shifted towards lower region and intensity also decreased, whichindicate that there is some interaction between PANI and the RHA.
Figure 1FT-IR spectrum of RHA
Figure 2FT-IR spectrum of PANI.
Figure 3 FT-IR spectrum of PANI-RHA.
Thermal properties of RHA, PANI and PANI- RHA nanocomposites
Figure (4) shows thermo gravimetric analysis of RHA,PANI and PANI-RHA. From the Figure, RHA show higher thermal stability and its char yield is about 90% at 750
oC. In the caseof PANI, a major weight loss observedat initial temperature of 10–130
◦C and over 340
◦C.
This may be,ejection of water molecules fromnanocomposites in the lower temperature and in
the higher temperature level, the Polyaniline chainstarted degradation. At above 550
oC, the
complete degradation of polyaniline takes place and its show in Figure.Onthe other hand, in case
of PANI-RHA nanocomposite, the major weight loss decrease was found at lower temperature
and over 340◦C. From the spectra, the thermal stability PANI-RHA is in between RHA and
PANI, which confirms the doping of RHA into PANI.
Figure 4 TGA of RHA, PANI and PANI-RHA nanocomposites TEM Analysis
The morphology behavior of PANI-RHA nanocomposites was analyzed by TEMand the
image is shown in the Figure.5. From TEM analysis, it was clearly seen that the RHA particles
were highly dispersed into the PANI matrix. These results indicate thatthe PANI-RHA
nanocomposites possess good interfacial interaction through the chemicalbonding. The
nanometer level dispersion ofPANI- RHA particles show enhanced on the thermal properties of
the polymer composites
Figure 5 TEM of PANI-RHA nanocomposites
Water absorption studies
0 5 10 15 20 25 30
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
Weight gain (mg)
Time (days) EP
EPR1.0
EPR3.0
EPR5.0
EPR7.0
